1. Field
The embodiments discussed herein are directed to a technology of lighting processing in three-dimensional graphics.
2. Description of the Related Art
Various proposals have conventionally made for three-dimensional graphics. For example, in a conventional technology disclosed in Japanese Patent Application Laid-Open Publication No. 2001-266177, the floor number of a building on a two-dimensional map is determined by probability calculations using the two-dimensional map and information concerning at least one of the material, the main use and the floor area of the building included in the accompanying building information to create a three-dimensional map.
In a conventional technology disclosed in Japanese Patent Application Laid-Open Publication No. 2002-298162, a three-dimensional model is generated in accordance with plural three-dimensional model patterns prepared in accordance with the information concerning the bottom shape and the height of a building in advance to display a three-dimensional view with a small computer system. In a conventional technology disclosed in Japanese Patent Application Laid-Open Publication No. 2005-56075, original three-dimensional map data are processed by dividing the data into scene graph data where the data structure of a three-dimensional map is expressed as a tree structure and drawing data for drawing objects included in the three-dimensional map, and a display area is specified by referring to the scene graph to execute display processing.
However, in the conventional technologies of above patent documents, even if an object to be drawn has an obviously simple shape like a typical building, since faithful calculation processing equivalent to that for a complicated arbitrary shape is executed when a graphic LSI performs lighting calculations, it is problematic that the calculation processing is slowed down. Although a normal vector must be applied to a piece of vertex information to perform the lighting calculations with the graphic LSI, a normal vector must be calculated each time from vertex coordinates in the case of application to which data such as a two-dimensional map are only input, which delays the processing. If a CPU performs the lighting calculations, it is problematic that the load of the CPU is excessively increased.
If the lighting calculations are sequentially executed as above, it is problematic that the performance is seriously reduced when needless calculations are included. On the other hand, although a system capable of concurrently performing the lighting calculations is less affected by the performance reduction due to needless calculations, it is problematic that the performance is comprehensively reduced since needless data transfer is generated. It is also problematic that wasteful power consumption is increased by needless lighting calculations.